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99% Oxygen Production with Zeolites and Pressure Swing Adsorption: Designs and Economic Analysis Blake Ashcraft Jennifer Swenton

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99% Oxygen Production with Zeolites and Pressure Swing Adsorption: Designs and Economic Analysis Blake Ashcraft Jennifer Swenton 9999%% OOxxyyggeenn PPrroodduuccttiioonn wwiitthh ZZeeoolliitteess aanndd PPrreessssuurree SSwwiinngg AAddssoorrppttiioonn:: DDeessiiggnnss aanndd EEccoonnoommiicc AAnnaallyyssiiss Presentation by: Blake Ashcraft Jennifer Swenton PPrroojjeecctt GGooaallss DDeevveelloopp aa ppoorrttaabbllee aanndd hhoossppiittaall aaiirr sseeppaarraattiioonn pprroocceessss//ddeevviiccee wwiitthh ssiillvveerr zzeeoolliitteess ttoo pprroodduuccee aa ccoonnttiinnuuoouuss ffllooww ooff 9999%% ooxxyyggeenn RReeccoommmmeenndd tthhee aapppplliiccaattiioonn ooff tthhee pprroocceessss//ddeevviiccee iinn ddiiffffeerreenntt mmaarrkkeettss DDeetteerrmmiinnee iiff pprroocceessss//ddeevviiccee wwiillll bbee pprrooffiittaabbllee iinn tthhoossee mmaarrkkeettss OOvveerrvviieeww Market for Purified Oxygen Air Separation Methods Adsorbent Materials Proposed Use of Technology Hospital Design Portable Design Consumer Utility and Preference Business Plan Risk Recommendations MMaarrkkeett ffoorr 9999%% OOxxyyggeenn Oxygen is the third most widely used chemical in the world Annual worldwide market of over $9 billion. MMaaiinn aapppplliiccaattiioonnss:: Medical oxygen for hospitals and individual use Industrial applications for refineries and processing plants OOxxyyggeenn iinn MMeeddiicciinnee Inhalation therapy During surgery to maintain tissue oxygenation under anesthesia Resuscitation of patients The treatment of such diseases as chronic obstructive pulmonary disease, pneumonia, and pulmonary embolism For the newborn experiencing respiratory distress syndrome The treatment of respiratory burns or poisoning by carbon monoxide and other chemical substances PPoorrttaabbllee OOxxyyggeenn CCoonncceennttrraattoorrss Currently no portable device capable of producing 99% oxygen continuously Portable oxygen cylinders with 99% oxygen lasts up to 8 hours Percentage of individuals suffering from lung diseases such as chronic obstructive pulmonary disease (COPD) is increasing COPD is 4th leading cause of death worldwide HHoossppiittaall UUnniitt LLaarrggee hhoossppiittaallss ssppeenndd aann eessttiimmaatteedd $$117700,,000000 ppeerr aa yyeeaarr oonn ooxxyyggeenn AApppprrooxxiimmaatteellyy 335500 llaarrggee hhoossppiittaallss iinn UUnniitteedd SSttaatteess OOnn--ssiittee uunniitt aalllloowwss ffoorr:: – unlimited supply of Oxygen – Annual savings AAiirr SSeeppaarraattiioonn Air is used as feed stock Oxygen is separated based on physical characteristics Must remove Nitrogen and Argon for 99% Oxygen purity AAiirr SSeeppaarraattiioonn MMeetthhooddss Cryogenic Distillation Membrane Separation Pressure Swing Adsorption (PSA) CCrryyooggeenniicc SSeeppaarraattiioonn CCrryyooggeenniicc SSeeppaarraattiioonn Leading process for producing 99% oxygen in bulk. Involves liquidifying air and distilling the liquid air to separate the Oxygen, Nitrogen, and Argon. Can be sold in a liquid form. 1 L of liquid Oxygen = 860 L of gaseous Oxygen CCrryyooggeenniicc SSeeppaarraattiioonn Drawbacks – Process uses large bulky equipment – Energy requirements are substantial unless demand is more than 60 tons of oxygen per a day – Liquid oxygen evaporates back into the atmosphere over time MMeemmbbrraanneess MMeemmbbrraanneess Permeable materials used to selectively separate Oxygen, Nitrogen, and Argon Large and medium scale production. Pressurized air is passed through the membrane and is separated by permeability characteristics of each component in relation to the membrane. MMeemmbbrraanneess Drawbacks Membranes require a large surface area to achieve high product flow rates. Large pressures are typically used – Safety hazard – Large compressors Oxygen and Argon molecules are similar in size and have similar permeability properties. – This results in a selectivity of ≈2.5 O2/Ar and a low oxygen recovery. PPrreessssuurree SSwwiinngg AAddssoorrppttiioonn PPrreessssuurree SSwwiinngg AAddssoorrppttiioonn Uses sorbents (zeolites, nanotubes) in two adsorption columns to separate molecules. Two columns allow for the process to operate semi- continuously. 4 Process stages – Adsorption/Production – Blowdown/Purge PPrreessssuurree SSwwiinngg AAddssoorrppttiioonn Stage 1 Compressed air is fed into the first bed. Nitrogen and argon molecules are trapped, while oxygen is allowed to flow through. PPrreessssuurree SSwwiinngg AAddssoorrppttiioonn Stage 2 The adsorbent in the first bed becomes saturated with nitrogen and argon molecules The airflow feed is directed into the second bed. PPrreessssuurree SSwwiinngg AAddssoorrppttiioonn Stage 3 The adsorbent adsorbs nitrogen and argon in the second bed. The first bed is depressurized allowing argon and nitrogen to be purged out of the system and released to the atmosphere. PPrreessssuurree SSwwiinngg AAddssoorrppttiioonn Stage 4 The process starts over. Compressed air is once again fed into the first bed. The second bed is depressurized releasing argon and nitrogen molecules to the atmosphere. AAddssoorrbbeennttss ffoorr PPSSAA Introduction to Zeolites and Carbon Nanotubes Structures Applications SSiilliiccaa GGeell PPrreettrreeaattmmeenntt Pretreatment bed to remove water vapor and impurities such as carbon dioxide – Air at 100% humidity is approximately 3% water vapor Water can impair the performance of adsorbents in the PSA adsorption columns. Silica gel beds are necessary to remove water vapor from the air. – A heating coil used to evaporate the water from the silica gel KKiinneettiicc SSeeppaarraattiioonn MMoolleeccuullaarr SSiieevvee CCaarrbboonn ((MMSSCC)) aaddssoorrbbeennttss uussiinngg PPSSAA tteecchhnnoollooggyy IIddeeaall ffoorr sseeppaarraattiioonn ooff AArrggoonn aanndd OOxxyyggeenn – MSCs in kinetic adsorption can adsorb Oxygen 30 times faster than Argon Creates a problem in design, requiring two PSA systems to collect the adsorbed Oxygen CCaarrbboonn NNaannoottuubbeess Sheets of carbon atoms rolled into tubes of varying diameters Nanotubes have extraordinary strength Potential uses in many industrial processes, including adsorption. CCaarrbboonn NNaannoottuubbeess Advantages Nanotubes have little interaction with nitrogen at high temperatures due to oxygen’s higher packing efficiency, smaller diameter, and entropic energies Research has shown that single walled carbon nanotubes (SWCN) of 12.53Å have a selectivity of O2/N2 of 100:1 at 10 bar. It has been indicated that Argon will have very little interaction with nanotubes CCaarrbboonn NNaannoottuubbeess Disadvantages Nanotubes are so efficient the volume of nanotubes required for separation of air is much smaller than the volume of feed air. – Nanotubes’ surface area is not large enough to react with the volume of air required. – No current way to disperse nanotubes effectively for PSA air separation Price range for nanotubes is $325 to $500 per gram ZZeeoolliitteess Microporous crystalline structures Lifespan of 10 years The zeolite’s structure governs which molecules are adsorbed. Various ways of controlling adsorption – separate molecules based on differences of size, shape and polarity ZZeeoolliitteess IIoonn EExxcchhaannggee:: Metal cations (calcium, sodium, silver) are bound to the zeolite structure – Silver cation zeolites have be proven to be best for air separation Creates an electrostatic interaction between the cation ion and the molecules being adsorbed LLiiAAggXX ZZeeoolliittee Useful for removing Nitrogen from Oxygen with product throughput .1 kg 02/hr/kg adsorbent. Can obtain 96.42% oxygen purity with 62.74% Oxygen recovery. Drawback is the selectivity of Argon to Oxygen is approximately 1:1. AAggAA ZZeeoolliittee Argon to Oxygen selectivity of 1.63 to 1 7 cm3/g of Argon adsorbed at atmospheric pressure Nitrogen to Oxygen selectivity of 5 to 1 0 1 1 FN 2 t L1 AN N 2 1 AN N 2 EEqquuiilliibbrriiuumm AAddssoorrppttiioonn TThheeoorryy Competition between the different molecules on the adsorbent sites exists. – Langmuirian Multi-component Theory is used to determine the fractional loading of each component on the adsorbent Selectivity describes how selective one component is to bind to the adsorbent over another component 0 1 1 FN 2 t L1 AN N 2 1 AN N 2 EEqquuiilliibbrriiuumm AAddssoorrppttiioonn TThheeoorryy Material Balances – Nitrogen – Oxygen – Argon 0 1 1 FN 2 t L1 AN N 2 1 AN N 2 EEqquuiilliibbrriiuumm AAddssoorrppttiioonn TThheeoorryy For the adsorption bed to remove both Nitrogen and Argon the velocity ratio of the argon front must be greater than that of the nitrogen front PPrrooppoosseedd UUssee ooff tthhee PPrreesseenntteedd TTeecchhnnoollooggiieess PPrrooppoosseedd UUssee ooff TTeecchhnnoollooggyy Pressure Swing Adsorption (PSA) will be used in the design for: – Medium scale capacity – Safety – Cost savings An analysis of 4 designs using zeolites LiAgX and AgA in the PSA adsorption beds was performed. The column diameter and cycle time was held constant. – Design 1 LiAgX zeolite – Design 2: AgA zeolite – Design 3: Mixed ratio of zeolites LiAgX and AgA – Design 4: Both LiAgX and AgA zeolites separating them DDeessiiggnn 11:: LLiiAAggXX zzeeoolliittee Nitrogen Removal – LiAgX removes nitrogen with a 96.42% purity Oxygen and 62.74% recovery. – The is the best zeolite for nitrogen removal Argon Removal – Argon to Oxygen selectivity of 1:1. – Requires a large volume of LiAgX zeolite to accomplish required purity Large volume of zeolite is required. Costs and inlet airflow rate increases. DDeessiiggnn 22:: AAggAA zzeeoolliittee Nitrogen Removal – Nitrogen to Oxygen selectivity of
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